Energy recovery ventilation control system

ABSTRACT

A control system comprising a temperature sensor, an enthalpy sensor and a processor capable of receiving said temperature and enthalpy signals and further capable of controlling the operation of an energy recovery ventilation wheel based at least in part on said temperature and enthalpy signals.

REFERENCE TO RELATED APPLICATIONS

This non-provisional application is a divisional patent application ofSer. No. 13/656,797 filed Oct. 22, 2012, which claims priority from U.S.provisional application Ser. No. 61/554,040 filed Nov. 1, 2011, whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This disclosure relates generally to air handling systems for buildings,more particularly to energy recovery ventilation systems, andspecifically to a temperature and/or enthalpy control for an energyrecovery wheel.

The present disclosure is directed to systems and methods which controlenergy recovery ventilation (ERV) systems of buildings. ERV systems maybe used to recover energy and lower utility expenses. Energy recoverywheels rotate between the incoming outdoor air and the exhaust air. Asthe wheel rotates, it transfers a percentage of the heat and moisturedifferential from one airstream to the other. The outdoor air ispre-conditioned reducing the capacity and energy needed from themechanical HVAC system. According to guidelines, building environmentsrequire a specific amount of fresh air to dilute contaminates in thespace and provide ventilation for high concentrations of people. Therequired amount of fresh air may provide dilution of contaminates, tominimize the possibility of “sick building syndrome.” Increasing theoutside air intake lowers the carbon dioxide levels in the building, andmay help keep the occupants alert and healthier. ERVs may also reduceindoor odors with fresh outside air that is brought into the building asstale air may be exhausted out of the building.

When fresh air is brought into a building, conditioned air from theinside may be exhausted to the outside to equalize pressure. The energyof the conditioned exhaust air leaving the building may be used topre-condition outside fresh air in the summer and winter. Whenconditions are suitable for free cooling in the spring and/or fall, theenergy recovery ventilator enters an economizer sequence.

An energy recovery ventilation wheel (wheel) may be used within an ERV.The rotating wheel heat exchanger may be composed of a rotating cylinderfilled with an air permeable material resulting in a large surface area.The surface area is the medium for the sensible and/or enthalpy energytransfer. As the wheel rotates between the ventilation and exhaust airstreams it picks up heat energy and releases it into the colder airstream. The driving force behind the exchange is the difference intemperatures between the opposing air streams. Typical media usedconsists of polymer, aluminum, and synthetic fiber.

The enthalpy exchange is accomplished through the use of desiccants.Desiccants transfer moisture through the process of adsorption which ispredominately driven by the difference in the partial pressure of vaporwithin the opposing air-streams. Typical desiccants consist of silicagel, and molecular sieves.

One disadvantage of using a wheel is moisture build up in and on thewheel. In one embodiment, a sequence of operation is undertaken, withinputs from the outside enthalpy and/or temperature to control theoperation of the sequence.

Representative of the art is U.S. Pat. No. 6,205,797 which discloses anair conditioning system and operation method, having dehumidificationability and flexibly adaptable for processing a variety of conditioningloads, and also energy conserving. The invention comprises a desiccantfor adsorbing moisture from process air, and a heat pump, including acompressor, that operates by using process air as a low-temperature heatsource and regeneration air as a high-temperature heat source so as tosupply heat to regeneration air for regenerating the desiccant.Processes of heat transfer in a sensible heat exchanger are madeadjustable, for exchanging heat between post-desiccant process air thathas not flowed into the low temperature heat source heat exchanger andpre-desiccant regeneration air that has not yet regenerated thedesiccant.

SUMMARY OF THE INVENTION

A control system comprising a temperature sensor, an enthalpy sensor anda processor capable of receiving said temperature and enthalpy signals,and further capable of controlling the operation of an energy recoveryventilation wheel, based at least in part on said temperature andenthalpy signals.

The foregoing has outlined rather broadly the features and technicaladvantages of the present disclosure in order that the detaileddescription of the disclosure that follows may be better understood.Additional features and advantages of the disclosure will be describedhereinafter which form the subject of the claims of the disclosure. Thenovel features which are believed to be characteristic of thedisclosure, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form part ofthe specification in which like numerals designate like parts,illustrate embodiments of the present disclosure and together with thedescription, serve to explain the principles of the disclosure. It is tobe expressly understood, however, that each of the figures is providedfor the purpose of illustration and description only and is not intendedas a definition of the limits of the present disclosure. In thedrawings:

FIG. 1 is a plan view of an energy recovery ventilation system;

FIG. 2 is a flowchart of a method according to an embodiment; and,

FIG. 3 is a schematic of an energy recovery ventilation control system,according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a general ERV system 100. System 100 may be an air-to-airtype heat exchanger. System 100 may include an energy recoveryventilation wheel, or thermal wheel, or enthalpy wheel (wheel) 110. Asthe wheel rotates between the ventilation 120 and exhaust air 130streams it may pick up heat energy and release it into the colder airstream. In different seasons the inside or the outside air may have moreheat or moisture or both and thereby more energy.

The system 100 in FIG. 1 may show an embodiment where the outside air120 is warmer than the inside air 140. As can be seen, the conditionedinside air that is being exhausted 130 may be mixed with the incomingoutside air 120, via a bypass opening 112 to lower the temperature andraise the relative humidity of the incoming outside air. A portion ofthe exhaust flow 130 may also pass thorough wheel 110 in addition toflowing through the bypass 112. Wheel 110 rotates to cool the incomingoutside air. This helps reduce the amount of energy used by the airconditioning and air handling system to bring the temperature down tothe set point of the system.

It will be appreciated that when the outside air is cooler and thebuilding is to be heated, the exhausted inside air will be used to warmthe incoming outside air using the wheel 110 and the bypass opening 112to reduce power consumption of the ERV.

System 100 may also include one or more blowers 114 a and 114 binstalled in ductwork adjacent to the wheel 110 to aid the exchange ofair to and from a building (not shown) in which the system operates.

FIG. 2 is a flow chart of a method 200 of operation of an ERV controlsystem, according to an embodiment. Method 200 may include the step ofreading the temperature and enthalpy from the respective sensors, andreading the temperature setpoints at 202. Temperature and enthalpyreadings are taken at the respective sensors and are received at acontroller. The temperature and enthalpy reading may be from inside oroutside the ERV, but are preferably from outside air entering the ERV.Reference to the “enthalpy reading” comprises sensing the relativehumidity of the air which is then combined with the temperature readingby the controller to determine an enthalpy in BTU/lbm. The enthalpysensor may also sense both dry bulb temperature and relative humidity.Examples include Honeywell part no. C7400A.

The controller may also have setpoints for temperature. This setpointmay be entered by a user through a user interface or come preset fromthe factory.

Method 200 may include the step of determining the operation mode at204. There may be different modes of operation of the system. In thisembodiment, there may be a temperature based operation, and enthalpybased operation, and a combined mode of operation. It will beappreciated that there may be many other modes of operation withoutstraying from the scope of this disclosure. The mode of operation may beselected by a user via pins and jumpers, or by another user interface.Furthermore, the mode may be determined by the sensor readings and thesetpoint from 202 above.

If it is determined that the temperature mode of operation is desired,control may flow to 208 where another determination is made. At 208, adetermination is made whether the temperature reading from the sensor islower than a high setpoint, and greater than a lower setpoint. If bothof these determinations are true, the relay to power the wheel is shutoff for a period of time (600 seconds in this embodiment) at 214. Thenthe wheel is turned on for a period of time (60 seconds in thisembodiment) at 216. The process may then start over at 202.

If the temperature is outside of the range defined in 208, the “NO” legis followed and the wheel is set to “ON”. The process may then startover at 202.

If it is determined at 204 that the enthalpy mode is desired, theprocess flows to 212. At 212 it is determined if the enthalpy from theenthalpy sensor is greater than a setpoint (60% RH in this embodiment).If it is then the process flows to the relay to power the wheel isturned OFF for a period of time (600 seconds in this embodiment) at 214.Then the wheel is turned ON for a period of time (60 seconds in thisembodiment) at 216. The process may then start over at 202.

If the enthalpy is not greater than 60% the “NO” leg is followed and thewheel is set to “ON” at 210. The process may then start over at 202.

If it is determined that the combined mode of operation is desired at204, control may flow to 218 where another determination is made. At208, a determination is made to see if the air temperature reading fromthe sensor is lower than a high setpoint (approximately 70° F./21° C.),and greater than a lower setpoint (approximately 40° F./4° C.) and ifthe enthalpy is greater than approximately 60%. If all of thesedeterminations are true, the relay to power the wheel is turned OFF fora period of time (600 seconds in this embodiment) at 214. Then the wheelis turned ON for a period of time (60 seconds in this embodiment) at216. The process may then start over at 202.

If the temperature or enthalpy is outside of the range defined in 218,the “NO” leg is followed and the wheel turned on at 220. The process maythen start over at 202.

This process may reduce the dust and moisture accumulation on the wheelwhen conditions are proper.

The system comprises a method of controlling operation of an energyrecovery ventilation wheel comprising, measuring the outside temperaturewith a temperature sensor, measuring the outside enthalpy with anenthalpy sensor, receiving a temperature signal at a processor from saidtemperature sensor, wherein said temperature signal is based at least inpart on the outside temperature, receiving an enthalpy signal at saidprocessor from said enthalpy sensor, wherein said enthalpy signal isbased at least in part on the outside enthalpy, and controlling theoperation of an energy recovery ventilation wheel by said processor,based at least in part on said temperature signal or said enthalpysignal or both, wherein said controlling comprises a sequence to reducea moisture buildup on said energy recovery ventilation wheel.

It will be appreciated that although this method is shown in aparticular order, any order of these steps are included in the scope ofthis disclosure.

FIG. 3 shows a system 300 which may be capable of the control of an ERVsystem, according to an embodiment. System 300 may include a temperaturesensor 302, an enthalpy sensor 304, a controller 306, and thermal wheel308, and one or more blowers 310. For example, blowers 310 wouldcorrespond to blowers 114 a and 114 b.

Temperature sensor 302 may be capable of sensing temperature andoutputting a temperature signal generally corresponding to thetemperature sensed. Similarly, enthalpy sensor 304 may be capable ofsensing enthalpy of the environment it is in, and outputting an enthalpysignal based at least in part on the enthalpy sensed.

System 300 may also include a controller 306. Controller 306 may becapable of receiving the temperature and enthalpy signals and convertingthe signals to information which may be used by the controller 306. Thecontroller 306 may use the information in calculation, comparisons,and/or in other programming. Controller 306 may include a processorcapable of running a computer program or the like.

Controller 306 may also be capable of controlling the operation ofthermal wheel 308 and blower(s) 310. Based at least in part on thetemperature and enthalpy signals received, controller 306 may controlthe operation of wheel 308 and blower(s) 310. Controller 306 may also becapable of receiving setpoints for ranges of temperature and enthalpy.These setpoints may be used to determine the operation and control ofthe wheel 308 and blower(s) 310.

The system 300 may have an “economizer” mode of operation. This may bewhen the outside air does not need to be conditioned as much. In thismode of operation the wheel 308 may be pivoted out of the airstream,which may eliminate the pressure needed to drive air through the wheel308, by blower(s) 310. This may reduce the amount of power used by theblower(s) 310.

When the wheel 308 is not in the airstream, dust and moisture mayaccumulate on the wheel 308. The present disclosure may includeoperation to reduce the dust and moisture buildup on the wheel. This maybe a start/stop/jog sequence of driving the wheel. It might also includean enclosure for containing the wheel to protect it from theenvironment.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods, and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. The disclosure disclosed herein may suitablybe practiced in the absence of any element that is not specificallydisclosed herein.

We claim:
 1. A method of controlling operation of an energy recoveryventilation wheel, comprising: measuring an outside air temperature witha temperature sensor; measuring an outside air enthalpy with an enthalpysensor; receiving a temperature signal at a processor from thetemperature sensor, wherein the temperature signal is based at least inpart on the outside air temperature; receiving an enthalpy signal at theprocessor from the enthalpy sensor, wherein the enthalpy signal is basedat least in part on the outside air enthalpy; and controlling theoperation of the energy recovery ventilation wheel with the processor,by: deactivating, with the processor, the energy recovery ventilationwheel for a first time period in response to the temperature signal, theenthalpy signal, or both, exceeding one or more set points; and inresponse to the energy recovery ventilation wheel being inactive for thefirst time period, reactivating, with the processor, the energy recoveryventilation wheel for a second time period, wherein reactivating theenergy recovery ventilation wheel results in full, continuous rotationof the energy recovery ventilation wheel.
 2. The method of claim 1,wherein the controlling further comprises activating a blower in thefirst time period while the energy recovery ventilation wheel isdeactivated.
 3. The method of claim 2, wherein the controlling furthercomprises reactivating the energy recovery ventilation wheel after atleast the first time period such that a moisture buildup on the energyrecovery ventilation wheel is removed.
 4. The method of claim 3, whereinreactivating the energy recovery ventilation wheel occurs at least 10minutes after the deactivating.
 5. The method of claim 1, wherein theone or more set points comprise a temperature set point of approximately40 degrees Fahrenheit.
 6. A method of controlling operation of an energyrecovery ventilation wheel, comprising: measuring an outside airtemperature with a processor based on input from a temperature sensor;measuring an outside air enthalpy with the processor by combining inputfrom a relative humidity sensor with the input from the temperaturesensor; and controlling the energy recovery ventilation wheel using theprocessor, by: turning off the energy recovery ventilation wheel, withthe processor, for a time period in response to the outside airtemperature, the outside air enthalpy, or both, being withinpredetermined ranges; and after the time period, turning on the energyrecovery ventilation wheel, with the processor, and causing full,continuous rotation of the energy recovery ventilation wheel.
 7. Themethod of claim 6, wherein the controlling comprises activating a blowerduring the time period.
 8. The method of claim 6, wherein, after thetime period, turning on the energy recovery ventilation wheel, with theprocessor, and causing full, continuous rotation of the energy recoveryventilation wheel is configured to remove a moisture buildup on theenergy recovery ventilation wheel.
 9. The method of claim 8, wherein thetime period is 10 minutes.
 10. The method of claim 6, wherein thepredetermined ranges comprise an outdoor air temperature range ofapproximately 40 degrees Fahrenheit to approximately 70 degreesFahrenheit.
 11. A method of controlling operation of an energy recoveryventilation wheel, comprising: measuring outside air parameters usingone or more sensors; communicating the outside air parameters from theone or more sensors to a processor; processing the outside airparameters with the processor; and controlling the energy recoveryventilation wheel using the processor, by: opening a relay, with theprocessor, such that power to the energy recovery ventilation wheel isdisconnected for a first time period when the outside air parameters arewithin predetermined ranges; and closing the relay, with the processor,after the first period, such that the power to the energy recoveryventilation wheel is connected, and the energy recovery ventilationwheel is reactivated for a second time period and rotates with full,continuous rotation.
 12. The method of claim 11, wherein the controllingcomprises activating a blower during the first time period.
 13. Themethod of claim 11, wherein closing the relay, with the processor, afterthe first period, such that the power to the energy recovery ventilationwheel is connected, and the energy recovery ventilation wheel isreactivated for a second time period and rotates with full, continuousrotation is configured to remove a moisture buildup on the energyrecovery ventilation wheel.
 14. The method of claim 13, wherein thefirst time period is 10 minutes.
 15. The method of claim 11, wherein theoutside air parameters comprise an air temperature, and wherein thepredetermined ranges comprise an air temperature range of approximately40 degrees Fahrenheit to approximately 70 degrees Fahrenheit.